CVE-2016-9409 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Admin control panel in MyBB (aka MyBulletinBoard) before 1.8.7 and MyBB Merge System before 1.8.7 might allow remote attackers to inject arbitrary web script or HTML via vectors involving pruning logs.
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Analysis
by VulDB Data Team • 08/08/2020
The CVE-2016-9409 vulnerability represents a critical cross-site scripting flaw discovered in MyBB, a widely used open-source bulletin board system. This vulnerability specifically affects the administrative control panel and impacts versions prior to 1.8.7 of both MyBB and its Merge System component. The flaw enables remote attackers to execute malicious scripts within the context of other users' browsers, potentially leading to unauthorized actions and data theft. The vulnerability manifests through vectors involving pruning logs, which are administrative functions used to manage and clean up forum data. This particular attack vector demonstrates how seemingly routine administrative operations can become entry points for sophisticated attacks.
The technical implementation of this XSS vulnerability stems from insufficient input validation and output sanitization within the administrative interface. When administrators or users interact with pruning logs functionality, the system fails to properly escape or filter user-supplied data before rendering it in web pages. This allows attackers to inject malicious JavaScript code, HTML content, or other harmful scripts that execute in the victim's browser context. The vulnerability is classified as a persistent XSS attack since the malicious content can be stored on the server and subsequently executed whenever affected pages are accessed. This particular flaw aligns with CWE-79, which describes improper neutralization of input during web page generation, a fundamental weakness in web application security. The attack pattern follows typical XSS methodologies outlined in the ATT&CK framework under T1059.007 for Scripting and T1566.001 for Phishing, where attackers leverage web application vulnerabilities to deliver malicious payloads.
The operational impact of this vulnerability extends beyond simple data theft, as it can enable complete compromise of administrator accounts and potentially the entire forum infrastructure. Attackers could manipulate forum content, steal user credentials, perform unauthorized administrative actions, and establish persistent backdoors within the system. The vulnerability is particularly dangerous because it targets the administrative control panel, which typically has elevated privileges and access to sensitive forum data. This creates a scenario where a successful attack could result in complete system compromise, data exfiltration, and potential use as a pivot point for attacking other systems within the network. The vulnerability affects not only the forum's integrity but also the trust of users who rely on the platform for secure communication and data exchange.
Mitigation strategies for CVE-2016-9409 require immediate implementation of the official security patches released by MyBB developers. Organizations should upgrade to version 1.8.7 or later, which includes proper input sanitization and output encoding mechanisms. Additionally, administrators should implement comprehensive input validation, employ Content Security Policy (CSP) headers, and regularly audit administrative interfaces for similar vulnerabilities. Network monitoring solutions should be configured to detect suspicious script injection attempts, and regular security assessments should be conducted to identify potential XSS vulnerabilities in web applications. The remediation process should also include user education about recognizing phishing attempts and suspicious forum activities, as well as implementing proper access controls and privilege separation within the administrative interface. Organizations should also consider deploying web application firewalls and implementing proper logging and monitoring of administrative activities to detect and prevent exploitation attempts.